* instead of free it immediately. The cluster will be freed
* after discard.
*/
- if (p->flags & SWP_PAGE_DISCARD) {
+ if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
+ (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
swap_cluster_schedule_discard(p, idx);
return;
}
* It's possible scan_swap_map() uses a free cluster in the middle of free
* cluster list. Avoiding such abuse to avoid list corruption.
*/
-static inline bool scan_swap_map_recheck_cluster(struct swap_info_struct *si,
+static bool
+scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
unsigned long offset)
{
+ struct percpu_cluster *percpu_cluster;
+ bool conflict;
+
offset /= SWAPFILE_CLUSTER;
- return !cluster_is_null(&si->free_cluster_head) &&
+ conflict = !cluster_is_null(&si->free_cluster_head) &&
offset != cluster_next(&si->free_cluster_head) &&
cluster_is_free(&si->cluster_info[offset]);
+
+ if (!conflict)
+ return false;
+
+ percpu_cluster = this_cpu_ptr(si->percpu_cluster);
+ cluster_set_null(&percpu_cluster->index);
+ return true;
+}
+
+/*
+ * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
+ * might involve allocating a new cluster for current CPU too.
+ */
+static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
+ unsigned long *offset, unsigned long *scan_base)
+{
+ struct percpu_cluster *cluster;
+ bool found_free;
+ unsigned long tmp;
+
+new_cluster:
+ cluster = this_cpu_ptr(si->percpu_cluster);
+ if (cluster_is_null(&cluster->index)) {
+ if (!cluster_is_null(&si->free_cluster_head)) {
+ cluster->index = si->free_cluster_head;
+ cluster->next = cluster_next(&cluster->index) *
+ SWAPFILE_CLUSTER;
+ } else if (!cluster_is_null(&si->discard_cluster_head)) {
+ /*
+ * we don't have free cluster but have some clusters in
+ * discarding, do discard now and reclaim them
+ */
+ swap_do_scheduled_discard(si);
+ *scan_base = *offset = si->cluster_next;
+ goto new_cluster;
+ } else
+ return;
+ }
+
+ found_free = false;
+
+ /*
+ * Other CPUs can use our cluster if they can't find a free cluster,
+ * check if there is still free entry in the cluster
+ */
+ tmp = cluster->next;
+ while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
+ SWAPFILE_CLUSTER) {
+ if (!si->swap_map[tmp]) {
+ found_free = true;
+ break;
+ }
+ tmp++;
+ }
+ if (!found_free) {
+ cluster_set_null(&cluster->index);
+ goto new_cluster;
+ }
+ cluster->next = tmp + 1;
+ *offset = tmp;
+ *scan_base = tmp;
}
static unsigned long scan_swap_map(struct swap_info_struct *si,
si->flags += SWP_SCANNING;
scan_base = offset = si->cluster_next;
+ /* SSD algorithm */
+ if (si->cluster_info) {
+ scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
+ goto checks;
+ }
+
if (unlikely(!si->cluster_nr--)) {
if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
si->cluster_nr = SWAPFILE_CLUSTER - 1;
goto checks;
}
-check_cluster:
- if (!cluster_is_null(&si->free_cluster_head)) {
- offset = cluster_next(&si->free_cluster_head) *
- SWAPFILE_CLUSTER;
- last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
- si->cluster_next = offset;
- si->cluster_nr = SWAPFILE_CLUSTER - 1;
- goto checks;
- } else if (si->cluster_info) {
- /*
- * we don't have free cluster but have some clusters in
- * discarding, do discard now and reclaim them
- */
- if (!cluster_is_null(&si->discard_cluster_head)) {
- si->cluster_nr = 0;
- swap_do_scheduled_discard(si);
- scan_base = offset = si->cluster_next;
- if (!si->cluster_nr)
- goto check_cluster;
- si->cluster_nr--;
- goto checks;
- }
-
- /*
- * Checking free cluster is fast enough, we can do the
- * check every time
- */
- si->cluster_nr = 0;
- goto checks;
- }
spin_unlock(&si->lock);
}
checks:
- if (scan_swap_map_recheck_cluster(si, offset))
- goto check_cluster;
+ if (si->cluster_info) {
+ while (scan_swap_map_ssd_cluster_conflict(si, offset))
+ scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
+ }
if (!(si->flags & SWP_WRITEOK))
goto no_page;
if (!si->highest_bit)
else
continue;
}
- count = si->swap_map[i];
+ count = ACCESS_ONCE(si->swap_map[i]);
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
}
{
struct swap_info_struct *si = swap_info[type];
struct mm_struct *start_mm;
- unsigned char *swap_map;
+ volatile unsigned char *swap_map; /* swap_map is accessed without
+ * locking. Mark it as volatile
+ * to prevent compiler doing
+ * something odd.
+ */
unsigned char swcount;
struct page *page;
swp_entry_t entry;
* reused since sys_swapoff() already disabled
* allocation from here, or alloc_page() failed.
*/
- if (!*swap_map)
+ swcount = *swap_map;
+ /*
+ * We don't hold lock here, so the swap entry could be
+ * SWAP_MAP_BAD (when the cluster is discarding).
+ * Instead of fail out, We can just skip the swap
+ * entry because swapoff will wait for discarding
+ * finish anyway.
+ */
+ if (!swcount || swcount == SWAP_MAP_BAD)
continue;
retval = -ENOMEM;
break;
spin_unlock(&swap_lock);
frontswap_invalidate_area(type);
mutex_unlock(&swapon_mutex);
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
vfree(swap_map);
vfree(cluster_info);
vfree(frontswap_map);
error = -ENOMEM;
goto bad_swap;
}
+ p->percpu_cluster = alloc_percpu(struct percpu_cluster);
+ if (!p->percpu_cluster) {
+ error = -ENOMEM;
+ goto bad_swap;
+ }
+ for_each_possible_cpu(i) {
+ struct percpu_cluster *cluster;
+ cluster = per_cpu_ptr(p->percpu_cluster, i);
+ cluster_set_null(&cluster->index);
+ }
}
error = swap_cgroup_swapon(p->type, maxpages);
error = 0;
goto out;
bad_swap:
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
set_blocksize(p->bdev, p->old_block_size);
blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
goto unlock_out;
count = p->swap_map[offset];
+
+ /*
+ * swapin_readahead() doesn't check if a swap entry is valid, so the
+ * swap entry could be SWAP_MAP_BAD. Check here with lock held.
+ */
+ if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
+ err = -ENOENT;
+ goto unlock_out;
+ }
+
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
err = 0;
projects / firefly-linux-kernel-4.4.55.git / blobdiff